Your guide to understanding waterproof clothing ratings and standards

The right waterproof clothing is key to keeping your team dry on the job.

Understanding different waterproof ratings helps you pick the best wet weather protection for your workforce. 

Not sure if a 5,000mm waterproof rating is high enough?

Can’t decide if your team needs water-resistant or waterproof gear?

We’ve got you covered! We break down everything you need to know about waterproof ratings and wet weather PPE standards.

WHAT ARE WATERPROOF RATINGS?

Waterproof ratings show how well a material keeps water out.

Measured in millimetres (mm), waterproof ratings show how much water pressure the fabric on the garment can withstand before leaking.

Here’s a comparison of different waterproof ratings: 

• 5,000mm and below - typically made from lightweight, water-resistant materials, and only stays dry during short, light showers.
• 5,000mm to 10,000mm - provides reliable wet weather protection in moderate to heavy rain.
• 10,000mm and over - suitable for prolonged use in heavy rain and snow.

From lightweight jackets to heavy-duty coveralls, waterproof ratings help you match clothing to your team's working conditions.

HOW IS WATERPROOFING MEASURED?

Waterproofing is measured using the Hydrostatic Head test. Put simply, it measures exactly how much water pressure a fabric can handle before water leaks through.

How the test is completed:

• The fabric is stretched under a sealed column of water.
• The pressure of the water is then increased until the fabric starts to let water in.
• The height of the water column at that point will then give the waterproof rating in millimetres.

The Hydrostatic Head test is part of the ISO 811 standard for textile water penetration. While there are no legal guidelines, 1,500mm is often considered the minimum benchmark for water-resistant materials. 

WHAT IS THE WATERPROOF STANDARD IN THE UK?

The EN 343 standard is the key benchmark for waterproof workwear in the UK. It doesn’t just test fabric, but the whole garment.

While the ISO 811 hydrostatic pressure test only measures how much water the fabric itself can withstand, EN 343 goes further. 

It looks at:

• Water resistance of fabric
• Water resistance of seams
• Garment construction and performance
• Breathability (how well sweat and moisture can escape)

This broader testing gives a more accurate picture of how the PPE will perform in real working conditions, not just in a lab.

UNDERSTANDING WATERPROOF CLASSES 

Instead of millimetre ratings, waterproofs tested to the EN 343 standard are categorised into three classes: Class 1, Class 2, and Class 3. 

Each garment has two class ratings: one for water resistance and one for breathability. Class 3:3 provides the highest protection.

Here’s what each class means:

WHAT IS THE CLASS 1 WATERPROOF RATING?

• Sweat can escape for up to one hour at 25°C.
• Seams/fabric not tested after washing or movement.
• Fabric and seams can withstand a minimum of 8,000 Pascals (Pa) before treatment.

Class 1 waterproofs are best for light showers and short wet spells.

WHAT IS THE CLASS 2 WATERPROOF RATING?

• Sweat can escape for up to 105 minutes at 25°C.
• Seams withstand 8,000 Pa before treatment but not after.
• Fabric can withstand a minimum of 8,000 Pascals (Pa) after treatment.

Class 2 waterproofs are good for longer exposure in moderate rain.

WHAT IS THE CLASS 3 WATERPROOF RATING?

• Sweat can escape for more than 3 hours at 25°C.
• Fabric withstands this same pressure after treatment.
• Fabric and seams can withstand 13,000 Pascals (Pa) before treatment.

Class 3 waterproofs are ideal for long hours spent working in heavy rainfall.

HOW TO FIND THE RIGHT WATERPROOF WORKWEAR 

UK outdoor workers face wet weather all year round.

Make sure your team stays dry throughout every season with the right waterproof workwear.

Before ordering, consider:

• How bad are the weather conditions?
• How long will your team be working outdoors? 
• Will a lower waterproof rating offer enough protection?
• Is the work physically demanding and likely to cause sweating?

Think about your team’s working day in detail to make sure you’re choosing the best waterproof PPE for the job.

TOP TIP: Choose waterproof and breathable workwear for team members performing strenuous tasks outdoors. 

WHEN IS WATERPROOF PPE NEEDED?

You need to provide waterproof PPE to all members of your team who are exposed to wet work conditions. 

Industries that often need waterproof PPE include:

• Utilities 
• Fishing 
• Forestry 
• Agriculture 
• Construction 

Stay compliant with the waterproof standard by providing PPE to team members working in rain, snow, and fog. Remember that you need to consider humidity, too. 

Even without rain, moisture-repellent clothing helps in humid workplaces.

KEEP YOUR TEAM DRY WITH SMI

Waterproof PPE keeps your team dry and protected from head to toe.

Switch to SMI to easily order all of your waterproof workwear in one place. 

We stock over 25,000 products, including waterproof coveralls, jackets, trousers, and water-resistant footwear.

Order before 5PM for next-day delivery. 

Need help choosing the right waterproofs for your team?

Give us a call on 0330 441 3500, or drop us a message today.

FAQS 

Is 3,000mm a good waterproof rating?

Clothing with a 3,000mm waterproof rating will keep you dry in light rainfall.

For heavier rain or longer exposure, outdoor clothing with a higher rating is a better choice. 

How can I tell if a jacket is waterproof?

To check if a jacket is waterproof, look for: 

• Taped seams
• Waterproof zips 
• Adjustable cuffs
• Waterproof coating 
• A waterproof rating in mm 
• The EN 343 classification on the label (for PPE jackets) 

Make sure to read the product description and check that it meets the EN 343 standard. 

Find high-quality and compliant waterproof jackets in the SMI shop. 

What is a good waterproof rating for clothing?

For heavy wet weather protection, make sure you choose clothes with a waterproof rating of 10,000mm or above. 

Clothing with this rating will keep you dry in heavy rain and snow. The higher the rating, the longer you’ll stay dry in poor weather conditions.